Nowadays, wireless network technologies have been utilized widely. In order to provide different qualities of service (QoS) in different environments, various wireless network system standards have been proposed. Among these wireless network system standards, WiMAX (Worldwide Interoperability for Microwave Access) standard and LTE (Long Term Evolution) standard have become popular wireless network system standards. In existing wireless network systems, when a wireless apparatus wants to establish a network connection or request resources for uplink transmission, the wireless apparatus would perform an uplink random access procedure with a base station in the wireless network system.
As shown in FIG. 1, conventional uplink random access procedures for a wireless network system usually comprise the following steps:                (1) the wireless apparatus 11 transmits a first uplink signal 102 with a preamble sequence on a random access channel (RACH) to the base station 13;        (2) the base station 13 receives the first uplink signal 102 and transmits a first downlink signal 104 with a random access response message to the wireless apparatus 11;        (3) the wireless apparatus 11 receives the first downlink signal 104 and transmits a second uplink signal 106 with a control message on an uplink shared channel (UL-SCH) to the base station 13; and        
(4) the base station 13 receives the second uplink signal 106 and transmits a second downlink signal 108 with a contention resolution message.
The above steps (i) and (ii) are used to adjust the transmission between the wireless apparatus and the base station. More specifically, the first uplink signal 102 is a reference signal for the base station 13 to generate some adjustment information, such as information for transmission power, frequency offset, timing alignment, etc. The first downlink signal 104 is an adjustment signal with the adjustment information for the wireless apparatus 11 to adjust its transmission parameters. In addition, the first downlink signal 104 also includes the allocation information for the wireless apparatus 11 to carry the control message on at least one resource block on the UL-SCH.
The control message carried by the second uplink signal 106 includes the identity (ID) of the wireless apparatus 11 and the information for requesting resources. The contention resolution message carried by the second downlink signal 108 is an acknowledgement that base station 13 has received the ID and accepted the requested resources. As the random access procedure has finished, the wireless apparatus 11 will transmit uplink data to the base station 13 through the requested resources.
In some cases, the wireless apparatus 11 may stay in the same or similar environment for a period of time. During the period of time, if the wireless apparatus 11 wants to request more resources, the wireless apparatus should perform the uplink random access procedure with the base station 13 again. However, the adjustment information carried by the first downlink signal 104 in the present uplink random access procedure maybe the same or almost same to the adjustment information carried by the first downlink signal 104 in the previous uplink random access procedure. Therefore, in these cases, the step (ii) would be a redundant step.
Accordingly, efforts still have to be made in this field to provide an appropriate uplink random access procedure for the aforementioned cases to improve the efficiency of the wireless network system.